Purification of concentrated oil solutions of polyvalent metal sulfonates



Patented Aug. 30, 1949 PURIFICATION OF CONCENTRATED OIL SO- LUTION S F POLYVALENT METAL SULFU- NATES Gordon W. Duncan, Westfield, and John C. Zimmer, Union, N. J., assignora' to Standard Oil Development Company, a corporation oiDelaware ,No Drawing. Application December 29, 1945, Serial No. 638,429

8 Claims. (Cl. 252-33) The present invention relates to lubricants and other petroleum products and more specifically to an improved method for the manufacture of additive compounds useful in rust preventives,

greases, engine oils and other compositions using Oil-soluble calcium and barium sulfonates 10 aromatics or their hydroxy derivatives, partially l5 hydrogenated aromatics, etc., with sulfuric acid or other sulfonating agents. fonic acids which are usually produced during the treatment of lubricating oil dlstillates with concentrated sulfuric acid (85% or higher con- 20.

centration) and which remain in the oil .after settling out sludge, are the most abundant and provide the preferred source of sulfonic acids. These sulfonic acids may be represented as However, the sulwhere (R) is 1 or more alkyl, alkaryl or aralkyl groups, and the aromatic nucleus may be a single or condensed ring or a partially hydrogenated ring. The most desirable sulfonic acids are those having molecular weights of 350 to 500, such as are formed when treating petroleum distillates having viscosities in excess of 90 S. U. S. at 210 F. with strong acid.

Sludge-free acid oil generally contains less than 15% dissolved sulfonic acids. These sulfonic acids can be converted directly into their calcium or barium salts by neutralizing the acids with an aqueous solution or suspension of the oxide, hy-

droxide or other alkaline-reacting salt or compound of calcium or barium, yielding oil solutions of calcium or barium sulfonate of up to about 15% concentration containing an excess of the neutralizing agent and by-products of the reaction, which are very diflicult to remove by ordinary purification procedures. However, a

15% oil solution of the oil-soluble metal sulfonate is not practical for use as an additive concentrate, and therefore methods of increasing the concentration of the sulfonate salts in the oil must be resorted to.

2 .acids from acid-treated oils and thus obtain sulfonates in concentrated form, is by neutralization with caustics, such as sodium or potassium hydioxide or carbonate to form alkali metal soaps which are extracted from the oil by solvents such as aqueous alcohol. After removing the solvent by distillation, leaving an oil solution of. the alkali metal sulfonate containing considerable water and inorganic salts, the soaps must again be dissolved in a solvent for the p rp se of settling out the inorganic salts in the form of brine which is discarded 'and the solvent again removed. by distillation, leaving a concentrate consisting of from 20 to ofv alkali metal soaps dissolved in oil. Where oil-soluble alkaline earth metal sulionates are desired, the alkali metal sulfonates are converted to the alkaline earth metal sulfonates by double decomposition of the alkali metal sulfonate with a salt, such as the chloride, or mixtures thereof with the oxide or hydroxide of the selected alkaline earth metal in aqueous solution.

Double decomposition of the alkali metal sulfonates with aqueous solutions ofsalts of the desired alkaline earth metal cangconveniently be carried out using the alcoholic: solution of the sulfonate obtained on extraction of the alkali neutralized acid 011. In this case a 10-30% aqueous solution of the alkaline earth metal salt, in an amount ill-% in excess or the theoretical amount required, is well mixed with the sulionate solution at substantially atmospheric temperature. The alkaline earth sulfonate, containing some alkali metal sulfonate, salts, oil and water, precipitates as a curdy mass. This mass is fiuxed with oil, dehydrated by heating to 275-325 F. and filtered free of insoluble material.

If the charge stock is the purified sodium sulionate concentrate in oil, it is adjusted to the desired final concentration by the addition of oil, and a 10-30% aqueous solution of alkaline earth metal salt in 10 to 100% excess of theoretical is emulsified with the oil phase. In some cases a small amount of the alkaline earth hydroxide is also incorporated to maintain alkalinity. The mixture is then heated to 275-325 F. todrive ofi the water and the product filtered toremove insoluble salts.

Although the products obtained by either of the above processes are clear and fluid, analyses indicate that they contain appreciable quantities of inorganic salts, apparently present as complexes with the sulfonate. This is shown by metal contents of up to 100% in excess of that re- The usual method employed to remove sulfonic 55 quired to neutralize the sulfonic acids and also by high contents of the acid radical or the salt l'phoric acid, oxalic acid, etc., which is capable of use to eflect double decomposition. While for/ some uses this complex compound is not objectionable and may sometimes even be desirable,

for certain other uses the non-sulfonate salt must be removed. An example is in the manufacture of the sulfonate greases disclosed .in our copending application, U. S. Serial No. 570,785, new Patent Number 2,455,970. issued July 13, 1943. While the above-mentioned contaminants may be removed by extensive water washing the emulsifiable nature of the sulfonate concentrate renders this operation difiicult it not impractical,

The principal object of the present invention is an improved method for the production of concentrates of oil-soluble alkaline earth metal sulionates. Another object is the provision of a method for removing impurities from oil solutions of alkaline earth metal sulfonates. These and other objects will be apparent to those skilled in the art upon reading the following description.

According to the present invention a process has been discovered by means of which oilsoluble alkaline earth metal Sulfonate concentrates free of excess alkaline earth metal compounds and inorganic salts can be prepared in'a rapid and efficient manner. Broadly speaking the objects of the present invention are accomplished by taking the crude reaction product resultlng from the double decomposition reaction between an oil-soluble alkali metal sulfonate and an alkaline earth metal compound in oil solution and treating it with aqueous inorganic acidic material capable of forming water-and oil-insoluble Salts with alkaline earth metals, until all excess alkaline earth metal is reacted. During this operation the hydrochloric acid or other acid formed by reaction of the inorganic salts present with the. added acid is evaporated by maintaining the mass at a temperature just below the decomposition temperature of sulfonic acids (170- 180 F.) and causing a reduction in efiective pressure either through the application of vacuum or through blowing with an inert gas. If need be the mass is then just neutralized with an alkaline earth metal hydroxide or carbonate and filtered to remove insoluble inorganic salts. Such procedure gives an oil concentrate of normal alkaline earth metal sulfonate of from 20-50% concentration, depending upon the concentration of alkali metal sulfonates in the original oil solution, substantially free of excess alkaline earth metal compounds and other inorganic salts.

' Accordingly, the present invention contemplates a process wherein a petroleum oil concentrate of alkali metal sulfonate containing 20-50% or more of the sulfonate, is reacted with an amount of alkaline earth compound, at least equal to 1 equivalent weight, based upon the amount of alkali metal sulfonate in the oil, in the form of a salt such as calcium chloride, barium chloride or strontium chloride, heating to a temperature of about 300 F. to complete the reaction, and eliminate water, and filtering to remove precipitated alkali metal chlorides. The resultant product is a solution of alkaline earth sulfonatechic-ride complex which is then ready for further treatment as subsequently described to obtain a substantially pure solution of alkaline earth metal sulfonate in oil. Alternatively, a previously formed concentrate of crude alkaline earth metal sulfonate in petroleum oil may be employed. The purification operation consists of treatment with an acid material such as suliuric acid, carbon dioxide, sulfur dioxide, phosforming waterand oil-insoluble salts with alka- "line earth metals, in a quantity sufflcient to re- I act with all the excess metal compounds present and warming, at subatmospheric pressure, if de- 1 sired, to a temperature of not more than 180 F. to drive oil volatile products.

, Blowing the mixture with the acid gases, or even inert gases, is helpful in driving oil hydrochloric acid formed.

If after warming and driving ofi volatile prod- A 30% oil solution of sodium sulfonate was emulsified with an aqueous solution of calcium chloride in 50% excess of theoretical, 0.5% calcium hydroxide was added, and the mixture heated to 300 F. and filtered. 200 g. of this clear calcium sulfonate solution in mineral lubricating oil, analyzing sodium 0.05%; calcium 1.71%; sulfur 2.13%, which corresponds to sodium sulfonate 1%; calcium sulfonate 29.2% and excess calcium 0.47%, was mixed with 20. cc. of 11% sulfuric acid, agitating to provide intimate contact. The mixture was heated to F., at atmospheric pressure for 30 minutes with carbon dioxide blowing to drive off hydrochloric acid formed from the excess calcium chloride used in making the calcium sulfonate. The mixture was then made neutral by the careful addition of aqueous calcium hydroxide, 0 g. of diatomaceous earth was added and the mixture heated to 300 F. and filtered. The filtrate analyzed sodium .026 calcium 1.21%; sulfur 2.15%, from which the calculated analysis is sodium sulfonate 0.5%; calcium sulfonate 29.7% and excess calciumnil.

Example 2 200 g. of the fluid calcium sulfonate-calcium chloride complex concentrate described in Example l was emulsified with 50 g. of water and the emulsion blow with sulfur dioxide gas at F. with mechanical agitation for 30 minutes. The product was heated to 300 F. to dehydrate it, filtered with 5% Hyflo filter aid, and a clear solid concentrate of normal calcium sulfonate was obtained. v

' Example 3 Example 2 was repeated employing carbon dioxide gas as the precipitating material and the sulfonate concentrate obtained showed an excess metal content of only 0.15%

What is claimed is:

1. Amethod of removing inorganic salt im- .;purities from an oil solution containing at least 20% of oil-soluble polyvalent metal sulfonates made by the double decomposition of alkali metal sulfonates and polyvalent metal compounds which comprises treating said all solution containing the reaction product produced during said double de composition reaction with an inorganic acidic material capable of forming water-insoluble salts with polyvalent metals and filtering to remove insoluble salts thus formed.

2. A method or removing excess calcium and some - other inorganic salts from oil solutions containing at least 20% of oil-soluble calcium metal sulionates made by the double decomposition of alkali metal suiionates and calcium compounds which comprises treating said oil solutions containingthe reaction product produced during said double decomposition with an inorganic acidic material capable of forming water-insoluble salts with said excess calcium.

3. A method of removing excess barium andlO other inorganic saltsfrom oil solutions contain ing at least 20% of oil-soluble barium sulionates made by the double decomposition of alkali metal sultonates and barium compounds which comprises treating said oil solutions containing a reaction product produced during said double decomposition reaction with an inorganic acidic material capable of formingwater-insoluble salts with barium and filtering to remove insoluble salts thus formed.

4. A method of removing excess alkaline earth metals and other inorganic salt impurities from an oilsolution containing at least 20% of oilsoluble alkaline earth metal sulfonates 'made by the double decomposition of alkali metal sul- 'Tonates and alkaline earth metal compounds which comprises treating said oil solution containing the reaction product produced during said double decomposition reaction withsufiicient suliuric acid to combine with the excess metal present, heating to a .temperature not higher than 180 F. under conditions adapted to drive oi! vola tile material, neutralizing with an alkaline earth metal carbonate and filtering to remove insoluble salts thus formed.

5. A method of removing excess alkaline earth metals and other inorganic salt impurities from an oil solution containing at least 20% of oilsoluble alkaline earth metal sulfonates made by the double decomposition of alkali metal suli'onates and alkaline earth. metal compounds which comprises heating said oil solution containing the reaction product to 180 F. under conditions adapted to drive of! volatile material which comprises heating said oil solution to a temperature of 180 F. and blowing the heated mixture with 7; The process of preparing a concentrated minera oil solution of oil soluble alkaline earth metal s ionates containing at least 20% or more oi. said sultonate, which comprises reacting a mineral all solution or alkali metal sulfonate of at least 20% concentration by weight with an aqueous alkaline earth metal salt, heating to a temperature and for a time sufllcient to evaporate the water and complete thereaction, filtering, treating with a'sufllcient quantity of an acidic material capable of forming water insoluble salts or said alkaline earth to' react with all the excess alkaline earth metal compounds present, and heating'moderately to drive oi! volatile acids formed by said last-mentioned reaction without decomposing said suli'onate.

8. Process as in claim? wherein said acid treated material is further neutralized with an alkaline earth basic. composition and filtered.

- GORDON W.'-DUNCAN.

JOHN C. ZIMMER.

mncanncss 10mm The following references are of record in the tile 0! this patent:

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Amott et al. Feb. 26, 1946 

